I have in fact never been ambushed by surprise smut. Though to be fair, I’m normally looking for it. Generally, smut is a selling point. I find it’s typically clearly labeled.
I have, however, been disappointed by surprise lack-of-smut. I feel that this is an injustice that needs to be rectified. People. If you’re writing a story that seems like it should have smut and then doesn’t? Please warn.